Method for Controlling Polishing Wafer

ABSTRACT

A method for controlling polishing a wafer includes the following step. Firstly, a database storing a number of status data of a polished film of a wafer and a number of polishing parameters corresponding to the status data is established. Each of the polishing parameters includes a head sweep of a polishing head along a redial direction of a polishing platen. The head sweep refers to a movement distance range from a center of the polishing head to a center of the polishing platen during a polishing process. Subsequently, a first wafer having a predetermined status data is provided. Thereafter, the predetermined status data is compared with the status data in the database so as to find out the polishing parameter corresponding to the predetermined status data, thereby determining a first polishing parameter of the first wafer. Afterward, a first polishing process using the first polishing parameter is applied to the first wafer. The method can control the status of a polished film and optimize the polishing parameter.

BACKGROUND

The present invention relates to a polishing process of a wafer, andparticularly to a method for controlling polishing a wafer.

With the development of semiconductor technology, it gradually becomes atrend to fabricate high density circuits on a wafer. Thus, it isnecessary for the wafer to have a metal film (e.g., a copper film) witha thin thickness and a high uniformity.

Generally, the metal film on the wafer is polished by a chemicalmechanical polishing (CMP) process. FIG. 1 is a schematic view ofpolishing a semiconductor wafer using a chemical mechanical polishingprocess. Referring to FIG. 1, a polishing head 10 is used to hold awafer 12 and to apply pressure to the wafer 12 so that the wafer 12 iscontacted with a polishing pad of a polishing platen (not shown) to bepolished. The polishing head 10 includes a retaining ring 11 forcontrolling pressure. The polishing head 10 can control a polishingspeed of the wafer 12 by applying different pressures to the wafer 12,thereby controlling a thickness distribution of a polished metal film onthe wafer 12. In general, the higher the pressure applied by thepolishing head 10 to the wafer 12 is, the faster the polishing speed ofthe wafer 12 is and the thinner the thickness of the polished metal filmon the wafer 12 is. However, nowadays, although the thin polished metalfilm can be obtained using the conventional chemical mechanicalpolishing process, the conventional chemical mechanical polishingprocess can not satisfy a thickness uniformity demand of polishing themetal film of the wafer 12.

In detail, during polishing the wafer 12 using the chemical mechanicalpolishing process, a polished region includes a number of annularregions, for example, a first region 121, a second region 122 and athird region 123. Because the third region 123 has a large area, infact, it is difficult to control the thickness uniformity of thepolished metal film in the third region 123 only using the polishingpressure. In addition, the pressure applied to the first region 121, thepressure applied to the second region 122 and the pressure applied tothe third region 123 by the polishing head 10 can only be eitherincreased or decreased simultaneously. Thus, the polishing speed in thefirst region 121, the polishing speed in the second region 122 and thepolishing speed in the third region 123 also can only be eitherincreased or decreased simultaneously correspondingly. That is, thepolishing head 10 can not adjust the polishing pressure according todifferent regions. Therefore, when the metal film of the wafer ispolished by a polishing process and is expected to have a specialthickness distribution for fabricating circuits, the above-mentionedmethod for controlling polishing the wafer is not satisfying.

BRIEF SUMMARY

The present invention provides a method for controlling polishing awafer so as to control a status of a polished film and optimize apolishing parameter.

To achieve the above-mentioned advantages, the present inventionprovides a method for controlling polishing a wafer including thefollowing step. Firstly, a database storing a number of status data of apolished film of a wafer and a number of polishing parameterscorresponding to the status data is established. Each of the polishingparameters includes a head sweep of a polishing head along a redialdirection of a polishing platen. The head sweep refers to a movementdistance range from a center of the polishing head to a center of thepolishing platen during a polishing process. Subsequently, a first waferhaving a predetermined status data is provided. Thereafter, thepredetermined status data is compared with the status data in thedatabase so as to find out a polishing parameter corresponding to thepredetermined status data, thereby determining a first polishingparameter of the first wafer. Afterward, a first polishing process usingthe first polishing parameter is performed to polish the first wafer.

In one embodiment provided by the present invention, the first polishingparameter includes a first head sweep, and the polishing head moves backand forth in the first head sweep along the redial direction of thepolishing platen during the first polishing process. In one embodimentprovided by the present invention, the polished film is a copper film.In one embodiment provided by the present invention, each of the statusdata is a thickness distribution of the polished film. In one embodimentprovided by the present invention, each of the status data is a removalrate distribution of the polished film.

In one embodiment provided by the present invention, the method forcontrolling polishing the wafer further includes the following step. Asecond wafer having the predetermined status data is provided.Subsequently, the first wafer polished by the first polishing process ismeasured to obtain a measuring status data of the first wafer.Thereafter, the measuring status data is compared with the predeterminedstatus data so as to obtain an amended status data to update the database. A polishing parameter corresponding to the amended status data isfound out in the updated data base, thereby determining a secondpolishing parameter of the second wafer. Afterward, a second polishingprocess using the second polishing parameter is performed to polish thesecond wafer.

In one embodiment provided by the present invention, in the step ofcomparing the measuring status data with the predetermined status data,a number of regions are defined on the first wafer so as to obtain acorrecting value of each of the regions. The correcting value of each ofthe regions is equal to a ratio of a status value of the measuringstatus data in each of the regions to a status value of thepredetermined status data in each of the regions. And the amended statusdata are equal to the status value of the measuring status data in eachof the regions is respectively multiplied by the correspondingcorrecting value.

In one embodiment provided by the present invention, the secondpolishing parameter includes a second head sweep, and the polishing headmoves back and forth in the second head sweep along the redial directionof the polishing platen during the second polishing process.

To achieve the above-mentioned advantages, the present invention alsoprovides a method for controlling polishing a wafer including thefollowing steps. At first, a number of wafers having an identicalpolished film are provided. Subsequently, the polished films of thewafers are polished sequentially using a number of polishing parameters.Each of the polishing parameters includes a head sweep of a polishinghead along a redial direction of a polishing platen. The head sweeprefers to a movement distance range from a center of the polishing headto a center of the polishing platen during a polishing process.Thereafter, the wafers are measured so as to obtain a number of statusdata of the polished films, thereby establishing a data base including arelationship of the status data and the polishing parameterscorresponding to the status data. Afterward, the database is stored inan advanced process control (APC) system. Then, a polishing process of awafer is controlled using the advanced process control system.

In the method for controlling polishing the wafer of the presentinvention, a database storing a number of status data of the polishedfilm of the wafer and a number of polishing parameters corresponding tothe status data is established. The data base is stored in the advancedprocess control system for controlling the polishing process of thewafer. Because each of the polishing parameters at least includes thehead sweep of the polishing head along the redial direction of thepolishing platen, the status of the polished film of the wafer, even thestatus of a partial region of the polished film of the wafer, can becontrolled by adjusting the head sweep of the polishing head along theredial direction of the polishing platen. Therefore, the method canoptimize the polishing parameter during the polishing process, therebyobtaining the satisfying polished film.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is a schematic view of polishing a wafer using a conventionalchemical mechanical polishing process.

FIG. 2 is a flow chart of a method for controlling polishing a wafer inaccordance with an embodiment of the present invention.

FIG. 3 is a schematic view of a polishing device for a polishing processin accordance with an embodiment of the present invention.

FIG. 4 is a schematic view of a number of polishing regions defined on awafer in accordance with an embodiment of the present invention.

FIGS. 5A˜5F are schematic views of a number of status data of a numberof wafers in accordance with another embodiment of the presentinvention, each of which is a thickness distribution of the polishedfilm of the wafer.

DETAILED DESCRIPTION

FIG. 2 is a flow chart of a method for controlling polishing a wafer inaccordance with an embodiment of the present invention. Referring toFIG. 2, in the present embodiment, the method for controlling polishinga wafer includes the following steps. Firstly, a database storing anumber of status data of a polished film of a wafer and a number ofpolishing parameters corresponding to the status data is established, asdescribed in the step 21. Each of the polishing parameters at leastincludes a head sweep of a polishing head along a redial direction of apolishing platen. The head sweep refers to a movement distance rangefrom a center of the polishing head to a center of the polishing platenduring a polishing process. In the present embodiment, the polished filmis, for example, a copper film.

In detail, in the step 21, at first, a number of wafers are provided.The wafers have an identical polished film (e.g., copper film). Then,the polished films of the wafers are polished sequentially using anumber of polishing parameters. That is, each of the wafers is polishedusing a corresponding polishing parameter. Further referring to FIG. 3,each of the polishing parameters includes a head sweep HS of a polishinghead 30 along a redial direction of a polishing platen 32. It is notedthat each of the polishing parameters can includes, for example, apolishing pressure, a polishing time, and so on. As shown in FIG. 3, thehead sweep HS refers to a movement distance range from a center Oh ofthe polishing head 30 to a center Op of the polishing platen 32 during apolishing process. The movement distance range is determined by theradius of the polishing head 30 and the radius of the polishing platen32 together. The polishing parameters can be chose in a manner such thatthe head sweep HS is either increased or decreased by a certain step. Inaddition, the polishing head 30 can move in a single erection in thehead sweep HS along the redial direction of the polishing platen 32during the polishing process. The polishing head 30 also can move backand forth in the head sweep HS along the redial direction of thepolishing platen 32 during the polishing process.

After the polished films of the wafers have been polished sequentiallyusing the corresponding polishing parameters, the polished films of thewafers are measured so as to obtain a number of status data of thepolished films corresponding to the polishing parameters. In the presentembodiment, each of the status data is a removal rate distribution ofthe polished film of each of the wafers.

The status data of the polished film of the wafers will be described asfollow. Further referring to FIG. 4, each of the wafers defines a numberof annular regions around a center of the wafer on the polished film,for example, from a region R1 to a region Rn (n is an integer). In thepresent embodiment, the head sweep HS is supposed to be in a range from5.3 inches to 8.3 inches. Thus, during polishing the waferssequentially, the head sweep HS can be increased by 0.5 inches step soas to obtain different polishing parameters to polish the wafers. As aresult, in the case of each of the head sweep HS, the status data fromthe region R1 to the region Rn of each of the wafers corresponding tothe head sweep HS can be obtained, thereby obtaining the removal ratedistribution of the polished film of each of the wafers. When a database is established, a number of removal rates of the polished film fromthe region R1 to the region Rn of are standardized. For example, astandardization value of the removal rate in the region R1 is equal to1, a standardization value of the removal rate in the region R2 is equalto a ratio of an absolute value of the removal rate in the region R2 toan absolute value of the removal rate in the region R1, and so on, astandardization value of the removal rate in the region Rn is equal to aratio of an absolute value of the removal rate in the region Rn to theabsolute value of the removal rate in the region R1. The absolute valueof the removal rate in the region R1 is an average value of the removalrates in the whole region R1, the absolute value of the removal rate inthe region R2 is an average value of the removal rates in the wholeregion R2, and so on, the absolute value of the removal rate in theregion Rn is an average value of the removal rates in the whole regionRn.

It is supposed that the number of the head sweep HS is m, and the numberof the wafers to be polished is also m. In the present embodiment, thehead sweep HS is supposed to be in a range from 5.3 inches to 8.3 inchesand is increased by 0.5 inches step during polishing the waferssequentially, so the m is equal to 6. Then, a data table is established,which includes the head sweeps and the standardization values of theremoval rates of the polished film of each of the wafers. In the case ofthe ith (i=1, 2, . . . m) head sweep HSi, the standardization values ofthe removal rates in the region Rj (j=1, 2, . . . n) of the wafer V(i,j)is defined. The established data table is shown as Table 1.

TABLE 1 Number HS(inches) Region R1 Region R2 . . . Region Rn 1 5.3~5.8V(1, 1) V(1, 2) . . . V(1, n) 2 5.8~6.3 V(2, 1) V(2, 2) . . . V(2, n) .. . . . . . . . . . . . . . . . . m 7.8~8.3 V(m, 1) V(m, 1) . . . V(m,n)

According to the data in the Table 1, a linearity simulation of the headsweep HSi and the standardization value of the removal rate of thepolished film in each region of the wafer V(i,j) can be performed,thereby obtaining a linear relationship formula, for example,Y=0.8X+0.2. In the formula, X refers to the number i of the head sweepHS, and Y refers to the standardization value of the removal rate of thepolished film in each region of the wafer V(i,j). It is noted that arelated coefficient R of the linearity simulation is generally relatedto the simulation degree of the linearity simulation. The larger therelated coefficient R of the linearity simulation is, the better thesimulation degree of the linearity simulation is. When R²>0.7, theexpected optimization linear relationship formula can be obtained. Adata base is established, which includes the status data (the removalrate distribution of the polished film) and the corresponding polishingparameters (the head sweep). Thus, a polishing parameter of a wafer tobe polished can be determined according to the data base. In the presentembodiment, the data base is stored in an advanced process controlsystem. A polishing process of the wafer to be polished is controlledusing the advanced process control system.

Controlling the polishing process of the wafer using the advancedprocess control system includes the following steps. Again, referring toFIG. 2, after the data base is established, a first wafer having apredetermined status data is provided, as shown in the step 22. In thepresent embodiment, the predetermined status data of the first wafer isa removal rate distribution of the polished film.

Thereafter, as shown in the step 23, the predetermined status data iscompared with the status data in the database stored in the advancedprocess control system. When the advance process control system hasfound out a status data matched with (i.e., identical to or similar to)the predetermined status data. The polishing parameter corresponding tothe matched status data (i.e., the predetermined status data) can be afirst polishing parameter of the first wafer. For example, the advancedprocess control system can find out a status data in the case of thesecond head sweep HS2 in the data base is matched with the predeterminedstatus data of the first wafer. Thus, the determined first polishingparameter of the first wafer includes the second head sweep HS2. Theadvanced process control system can control a polishing device toperform a first polishing process using the determined first polishingparameter to polish the first wafer, as shown in the step 24. In thefirst polishing process, the second head sweep HS2 is a first head sweepof the first polishing parameter of the first wafer. The polishing head30 can moves back and forth in the first head sweep along the redialdirection of the polishing platen 32 during the first polishing process.

In order to optimize the polishing parameter, the method for controllingpolishing the wafer further includes the following steps. As shown inthe step 25, a second wafer is provided. The second wafer has thepredetermined status data identical to the predetermined status data ofthe first wafer. That is, in the preset embodiment, the predeterminedstatus data of the second wafer is a removal rate distribution of thepolished film. The removal rate distribution of the polished film of thesecond wafer is identical to the removal rate distribution of thepolished film of the first wafer.

After the first wafer is polished by the first polishing process, theadvanced process control system controls a measuring device to measurethe polished first wafer so as to obtain a measuring status data of thefirst wafer. The measuring status data is a measuring removal ratedistribution of the polished film of the first wafer. The measuringstatus data will be feed back to the advanced process control system.The measuring device can be disposed according to the status data to bemeasured. In the present embodiment, the measuring device for measuringthe removal rate of the polished film is applied.

Then, as shown in the step 27, according to the data base stored in theadvanced process control system, the measuring status data is comparedwith the predetermined status data of the second wafer so as to obtainan amended status data to update the data base. A polishing parametercorresponding to the amended status data can be found out in the updateddata base, thereby determining a second polishing parameter of thesecond wafer.

In detail, in the step 27, a correcting value Uj (j=1, 2, . . . n) ofthe removal rate in the region Rj (j=1, 2, . . . n) of the polished filmof the first wafer can be obtained respectively. The correcting value Uj(j=1, 2, . . . n) of the removal rate in the region Rj (j=1, 2, . . . n)can be equal to a ratio of a status value of the measuring status datain the region Rj (j=1, 2, . . . n) to a status value of thepredetermined status data in the region Rj (j=1, 2, . . . n). Theamended status data can be calculated by the measuring status data andthe correcting value Uj (j=1, 2, . . . n) of the removal rate in theregion Rj (j=1, 2, . . . n). In the present embodiment, the amendedstatus data are equal to the status value of the measuring status datain each of the regions is respectively multiplied by the correspondingcorrecting value. The amended status data can be calculated by themeasuring status data and the correcting value Uj (j=1, 2, . . . n) ofthe removal rate. In the present embodiment, the amended status data areequal to the status value of the measuring status data in the region Rj(j=1, 2, . . . n) of the first wafer is respectively multiplied by thecorresponding correcting value Uj (j=1, 2, . . . n) of the removal rate.

For example, in the present embodiment, the measuring device measuresthe status data of the polished film of the first wafer so as to obtaina number of standardization values of the measured removal rates fromthe region R1 to the region Rn of the first wafer. That is, the statusvalues from the region R1 to the region Rn of the first wafer are thestandardization values of the measured removal rates from the region R1to the region Rn. According to the standardization values of themeasured removal rates from the region R1 to the region Rn of the firstwafer, the V(i,j) corresponding to the first polishing parameter can berefreshed and updated, thereby obtaining Vnew(i,j). For example, in thedata base, in the case of the second head sweep HS2, the standardizationvalue of the removal rate V(2,2) in the region R2 is 1.2 and thestandardization value of the measured removal rate in the region R2 is1.3. As a result, in the updated data base, in the case of the secondhead sweep HS2, Vnew (2,j)=1.3/1.2*V(2,j), j=1, 2, . . . n. Meanwhile,the linear relationship formula of the head sweep HS and thestandardization value of the removal rate of the polished film in eachregion of the wafer is also updated according to the update database.Thus, the second head sweep HS2 corresponding to the amended status datacan also be refreshed and updated, thereby optimizing the second headsweep HS2. It is noted that above-motioned description is only anexample of the region R2 of the wafer. In fact, the other regions of thefirst wafer can be performed a correction similar to the region R2 so asto refresh and update the whole data base.

Accordingly, the advance process control system can found out apolishing parameter (e.g., the refreshed and updated second head sweepHS2) corresponding to the amended status data in the updated data base.The polishing parameter (e.g., the refreshed and updated second headsweep HS2) corresponding to the amended status data in the updated database can be a second polishing parameter of the second wafer. Thus, theadvanced process control system can control the polishing device toperform a second polishing process using the second polishing parameterto polish the second wafer, as shown in the step 28. In the secondpolishing process, the refreshed and updated second head sweep HS2 is asecond head sweep of the second polishing parameter of the second wafer.The polishing head 30 can moves back and forth in the second head sweepalong the redial direction of the polishing platen 32 during the secondpolishing process.

It is noted that, the status data of the polished film of the wafer canbe represented by other status value except the removal ratedistribution of the polished film. For example, a removal thicknessdistribution of the polished film or a thickness distribution of thepolished film (i.e., a remaining thickness distribution of the polishedfilm) can be the status data of the polished film. Referring to FIGS. 5Ato 5F, the status data of the polished film of each of the wafers is athickness distribution of the polished film (i.e., the remainingthickness distribution of the polished film) in accordance with anotherembodiment of the present invention. The data base is established usingthe thickness distributions of the polished film and the correspondinghead sweep HS. In the present embodiment, similarly, the advancedprocess control system is applied to control the polishing process ofthe polished film of the wafer. The controlling steps are similar to thecontrolling steps the first embodiment and are not described here.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein, including configurations ways of the recessed portionsand materials and/or designs of the attaching structures. Further, thevarious features of the embodiments disclosed herein can be used alone,or in varying combinations with each other and are not intended to belimited to the specific combination described herein. Thus, the scope ofthe claims is not to be limited by the illustrated embodiments.

1. A method for controlling polishing a wafer, comprising: establishinga database storing a plurality of status data of a polished film of awafer and a plurality of polishing parameters corresponding to thestatus data, each of the polishing parameters at least comprising a headsweep of a polishing head along a redial direction of a polishingplaten, the head sweep referring to a movement distance range from acenter of the polishing head to a center of the polishing platen duringa polishing process; providing a first wafer having a predeterminedstatus data; comparing the predetermined status data with the statusdata stored in the database so as to find out a polishing parametercorresponding to the predetermined status data, thereby determining afirst polishing parameter of the first wafer; and performing a firstpolishing process using the first polishing parameter to polish thefirst wafer.
 2. The method as claimed in claim 1, wherein the firstpolishing parameter comprises a first head sweep, and the polishing headmoves back and forth in the first head sweep along the redial directionof the polishing platen during the first polishing process.
 3. Themethod as claimed in claim 1, wherein the polished film is a copperfilm.
 4. The method as claimed in claim 1, wherein each of the statusdata is a thickness distribution of the polished film.
 5. The method asclaimed in claim 1, wherein each of the status data is a removal ratedistribution of the polished film.
 6. The method as claimed in claim 1,further comprising: providing a second wafer having the predeterminedstatus data; measuring the first wafer polished by the first polishingprocess to obtain a measuring status data of the first wafer; comparingthe measuring status data with the predetermined status data so as toobtain an amended status data to update the data base, thereby findingout a polishing parameter corresponding to the amended status data inthe updated data base to determine a second polishing parameter of thesecond wafer; and performing a second polishing process using the secondpolishing parameter to polish the second wafer.
 7. The method as claimedin claim 6, wherein in the step of comparing the measuring status datawith the predetermined status data, a plurality of regions are definedon the first wafer so as to obtain a correcting value of each of theregions, the correcting value of each of the regions is equal to a ratioof a status value of the measuring status data in each of the regions toa status value of the predetermined status data in the correspondingregion, and the amended status data are equal to the status value of thepredetermined status data in each of the regions respectively multipliedby the corresponding correcting value.
 8. The method as claimed in claim6, the second polishing parameter comprises a second head sweep, and thepolishing head moves back and forth in the second head sweep along theredial direction of the polishing platen during the second polishingprocess.
 9. The method as claimed in claim 6, wherein each of the statusdata is a thickness distribution of the polished film.
 10. The method asclaimed in claim 6, wherein each of the status data is a removal ratedistribution of the polished film.
 11. A method for controllingpolishing a wafer, comprising: providing a plurality of wafers, thewafers having an identical polished film; polishing the polished filmsof the wafers sequentially using a plurality of polishing parameters,each of the polishing parameters comprising a head sweep of a polishinghead along a redial direction of a polishing platen, the head sweepreferring to a movement distance range from a center of the polishinghead to a center of the polishing platen during a polishing process;measuring the polished wafers so as to obtain a plurality of status dataof the polished films; establishing a data base comprising arelationship of the status data and the polishing parameterscorresponding to the status data; storing the database in an advancedprocess control system; and controlling a polishing process of a waferusing the advanced process control system.
 12. The method as claimed inclaim 11, wherein each of the status data is a thickness distribution ofthe polished film.
 13. The method as claimed in claim 11, wherein eachof the status data is a removal rate distribution of the polished film.14. The method as claimed in claim 11, wherein the step of controllingthe polishing process of the wafer using the advanced process controlsystem comprises: providing a first wafer having a predetermined statusdata; finding out a polishing parameter corresponding to thepredetermined status data in the database using the advanced processcontrol system according to predetermined status data, therebydetermining a first polishing parameter of the first wafer; andcontrolling a polishing device using the advanced process control systemto perform a first polishing process using the first polishing parameterto polish the first wafer.
 15. The method as claimed in claim 14,wherein the step of controlling the polishing process of the wafer usingthe advanced process control system further comprises: providing asecond wafer having the predetermined status data; controlling ameasuring device using the advanced process control system to measurethe first wafer polished by the first polishing process, therebyobtaining a measuring status data of the first wafer to feed back to theadvanced process control system; comparing the measuring status datawith the predetermined status data using the advanced process controlsystem so as to obtain an amended status data to update the data base,thereby finding out a polishing parameter corresponding to the amendedstatus data in the updated data base to determine a second polishingparameter of the second wafer; and controlling the polishing deviceusing the advanced process control system to perform a second polishingprocess using the second polishing parameter to polish the second wafer.16. The method as claimed in claim 9, wherein in the step of comparingthe measuring status data with the predetermined status data, aplurality of regions are defined on the first wafer so as to obtain acorrecting value of each of the regions, the correcting value of each ofthe regions is equal to a ratio of a status value of the measuringstatus data in each of the regions to a status value of thepredetermined status data in the corresponding region, and the amendedstatus data are equal to the status value of the predetermined statusdata in each of the regions respectively multiplied by the correspondingcorrecting value.